Intravitreal Injection of tPA Entraped in Liposomes, in Experimental Retinal Vein Photothrombosis

Abstract

Abstract: : Purpose: To evaluate the use of tPA entraped in liposomes, in an experimental rabbit model of retinal vessel photothrombosis. Methods: tPA was encapsulated in liposomes prepared by the DRV (dried–reconstituted vesicle) method (43 – 660 ug tPA / ml liposomes). Intravitreal injection liposome encapsulated t–PA (5–30 ug) was performed in the right eye of 11 rabbits after the animals retinal vessels had been thrombosed using a photodynamic technique.Retinal vessels of the fellow eyes were thrombosed and tPA without liposomes was also injected intravitreally in amounts of 15, 50 and 100 ug. Results: Retinal vessels remain occluded 18 hours after intravitreal injection of 15, 50 and 100 ug tPA. The injection of 100 ug tPA induced PVD. 5 of 11 eyes that received tPA entraped in liposomes exhibited reestablishment of blood column in retinal veins during biomicroscopy along with micro–haemorrhages. Immunohistochemistry showed that tPA entraped in liposomes can penetrate the lumen of small veins but not that of arteries. Conclusions:t–PA encapsulated in liposomes seems to be able to penetrate the lumen of small veins. Our preliminary data indicate that intravitreal injection of liposome entrapped t–PA may be effective in dissolving experimentally induced retinal vein thrombosis.

Keywords: vascular occlusion/vascular occlusive disease • immunohistochemistry • pharmacology